If there is assert() in script, function call for assert() is issued at execution. (If assert is not active, it returns TRUE simply)
It may be nice if there is "--disable-assert" option so that disable assert() function calls completely for production script. Especially if there are MANY assert() in scripts. I don't see any reason to call assert() for production scripts just to return TRUE, even if it a little overhead.
(I'll use a perl script that comments out all assert() from production scripts for the time being. There are more than 500 assert in my scripts :)
There are sevral options
1) Change zend_compile.c
2) Change zend_execute.c
3) Implement assert in Zend
4) Leave as it is. Educate users to comment out assert() for production scripts.
5) Leave as it is. Because it doesn't hart performance much.
6) Other?
It seems this can be done with little change
ZEND_DO_FCALL to ignore assert() in zend_execute.c
or
"zend_do_begin_function_call" to ignore assert() in zend_compile.c
1) or 2) may be easier to implement, but it breaks concept of modulality. 3) is most preffered. 4) is good enough, since it's trivial text subsutitution.
What do you think?

This is a good idea, there is currently an RFC in progress to address this issue exactly, and you yourself are involved in the conversation regarding solutions to better assertion still 14 years later ... props to you.
I'm going to mark as won't fix, this kind of change requires an RFC today.
This report can still be found and will be referenced by the current RFC.
Sorry about the wait.